Use of tetrahydrobenzoxazines as stabilisers

ABSTRACT

The use of tetrahydrobenzoxazines I 
                         
where R 1  is a hydrocarbyl radical and R 2 , R 3 , R 4  and R 5  are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals, and where R 2  to R 5  may also form a second and a third tetrahydrooxazine ring, with the proviso that at least one of the substituents has from 4 to 3000 carbon atoms and the remaining substituents, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms, as stabilizers for stabilizing inanimate organic material, especially turbine fuels, against the action of light, oxygen and heat.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 11/996,078, filed Jan. 18, 2008, the disclosure of which is incorporated herein by reference in its entirety. The parent application is the National stage of PCT/EP06/064352, filed Jul. 18, 2006, the disclosure of which is incorporated herein by reference in its entirety. The parent application claims priority to German Application No. 102005035527.7, filed Jul. 26, 2005, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to the use of specific tetrahydrobenzoxazines as stabilizers for stabilizing inanimate organic material against the action of light, oxygen and heat, especially in turbine fuels (jet fuels). The present invention further relates to a turbine fuel composition and to an additive concentrate for turbine fuels which comprise these tetrahydrobenzoxazines. The present invention further relates to a process for preparing these tetrahydrobenzoxazines. Since some of these tetrahydrobenzoxazines are novel substances, the present invention also relates to these novel substances themselves.

The mechanical, chemical and/or esthetic properties of inanimate organic material, for example of plastics and coatings, but also of mineral oil products and fuels, are known to be impaired by the action of light, oxygen and heat. This impairment is exhibited typically in the form of yellowing, discoloration, crack formation or embrittlement of the material. Stabilizers or stabilizer compositions with which improved protection against such impairment of organic material by light, oxygen and heat can be achieved are already known.

For instance, WO 05/073152 (1) describes 2-alkylpolyisobutenylphenols and their Mannich adducts as antioxidants for stabilizing inanimate organic material against the action of light, oxygen and heat. Other materials to be stabilized include fuels such as gasoline fuels, diesel fuels and turbine fuels, and also lubricant compositions. In turbine fuels, these 2-alkylpolyisobutenylphenols and their Mannich adducts bring about an improvement in the thermal stability and a reduction in the deposits in the fuel circuit and combustion system of the turbines.

WO 03/106595 (2) also discloses, as well as hydrocarbyl-substituted succinic acid derivatives and polyalkenylthiophosphonate esters, Mannich adducts made from hydrocarbyl-substituted phenols, an aldehyde and an amine as additives for turbine fuels (jet fuels) for improving the thermal stability and for reducing deposits.

However, especially for the mineral oil product and fuel sector, there is a need for stabilizers and antioxidants with improved protective action against the impairment of the material properties by light, oxygen and heat. For turbine fuels (jet fuels) in particular, which are exposed to extreme thermal stress during and before the combustion operation in turbines, for example in aviation turbines, novel improved stabilizers are being sought. In the turbines, these should simultaneously also reduce deposits in the fuel circuit and in the combustion system by virtue of their mode of action as antioxidants and/or dispersants.

It was therefore an object of the invention to provide stabilizers with an improved stabilization of inanimate organic material, especially of mineral oil products and fuels, in particular of turbine fuel, against the action of light, oxygen and heat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Accordingly, the use of tetrahydrobenzoxazines of the general formula I

in which the substituent R¹ represents a hydrocarbyl radical which has from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where R⁶ represents a hydrogen atom or a C₁- to C₄-alkyl radical, and the substituents R², R³, R⁴ and R⁵ are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where the substituent R⁴ may also be a radical of the formula Y

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituent X is a hydrocarbon bridging element which consists of one or more isobutene units or comprises one or more isobutene units, or where the substituent R⁴ may also be a radical of the formula Z or Z′

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituents R¹⁰ and R¹¹ may be the same or different and represent hydrogen or a C₁- to C₁₀-alkyl radical, and in which the substituents R² and R³ or R³ and R⁴ or R⁴ and R⁵, together with the part-structure —O—CH₂—NR⁷—CH₂— attached to the benzene ring, may also form a second tetrahydrooxazine ring, or the substituents R² and R³ and R⁴ and R⁵, together with the part-structures —O—CH₂—NR⁷—CH₂— and —O—CH₂—NR⁸—CH₂— attached to the benzene ring, may also form a second and a third tetrahydrooxazine ring, where R⁷ and R⁸ are each independently hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, with the proviso that at least one of the substituents R¹, R², R³, R⁴, R⁵, R⁷ or R⁸ has from 4 to 3000 carbon atoms and the remaining substituents from the group of R¹, R², R³, R⁴, R⁵, R⁷ and R⁸, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms, as stabilizers for stabilizing inanimate organic material against the action of light, oxygen and heat has been found.

Tetrahydrobenzoxazines are known in principle as additives for fuel and lubricant compositions. For instance, WO 01/25293 (3) and WO 01/25294 (4) disclose tetrahydrobenzoxazines with relatively long-chain radicals such as polyisobutenyl radicals which are situated as substituents on the benzene ring as gasoline fuel detergents which clean the valves and keep them clean. In the preparation processes disclosed in (3) and (4), these tetrahydrobenzoxazines are obtained as mixtures with the corresponding open-chain Mannich adducts of the parent phenol and also used thus in the gasoline fuels.

The preparation of tetrahydrobenzoxazines with short-chain substituents which are suitable, for example, as crop protection compositions, composed of 4-alkylphenols and an adduct of, for example, 1 mole of cyclohexylamine and 2 moles of formaldehyde or paraformaldehyde in methanol or ethanol as a solvent is described in U.S. Pat. No. 2,806,031 (5) and U.S. Pat. No. 3,132,960 (6).

The structural peculiarity of the tetrahydrobenzoxazines I to be used in accordance with the invention is that they comprise at least one relatively long-chain hydrocarbyl radical having from 4 to 3000 carbon atoms as one of the substituents R¹, R², R³, R⁴, R⁵, R⁷ or R⁸, either on the benzene ring or on an oxazine ring. In a preferred embodiment, this relatively long-chain hydrocarbyl radical having from 4 to 3000 carbon atoms is a polyisobutenyl radical. In a further preferred embodiment, the relatively long-chain hydrocarbyl radical may also be a C₁₆- to C₂₀-alkyl or -alkenyl radical. In particular, this relatively long-chain hydrocarbyl radical, which is preferably a polyisobutenyl radical or a C₁₆- to C₂₀-alkyl or -alkenyl radical, is situated on an oxazine ring, i.e. it occurs as substituent R¹ or R⁷ or R⁸. This relatively long-chain hydrocarbyl radical, which is preferably a polyisobutenyl radical or a C₁₆- to C₂₀-alkyl or -alkenyl radical, is preferably also situated on the benzene ring as substituent R² or R⁴. This relatively long-chain hydrocarbyl radical, which is preferably a polyisobutenyl radical or a C₁₆- to C₂₀-alkyl or -alkenyl radical, comprises preferably from 16 to 3000, especially from 20 to 1000, in particular from 25 to 500, most preferably from 30 to 250 carbon atoms. In the case of polyisobutenyl radicals, they preferably have number-average molecular weights M_(n) of from 200 to 40 000, preferably from 500 to 15 000, especially from 700 to 7000, in particular from 900 to 3000, most preferably from 900 to 1100.

Suitable C₁₆- to C₂₀-alkyl or -alkenyl radicals are appropriately the radicals of corresponding saturated or unsaturated fatty alcohols having from 16 to 20 carbon atoms. Mention should be made here in particular of n-hexadecyl (palmityl), n-octadecyl (stearyl), n-eicosyl, oleyl, linolyl and linolenyl, which usually occur as technical mixtures with one another owing to their natural origin.

The relatively long-chain hydrocarbyl radical having from 4 to 3000 carbon atoms mentioned may also be present in the tetrahydrobenzoxazines I more than once, for example twice or three times. When it occurs twice, this relatively long-chain hydrocarbyl radical, which is preferably a polyisobutenyl radical and/or a C₁₆- to C₂₀-alkyl or -alkenyl radical, occurs, for example, as substituent R¹ and R⁴ or R¹ and R⁷.

In a preferred embodiment, one or two polyisobutenyl radicals having a number-average molecular weight M_(n) of from 200 to 40 000 occur in the molecule as substituents R¹ and/or R² and/or R⁴ and/or R⁷ and/or R⁸.

The remaining substituents from the group of R¹, R², R³, R⁴, R⁵, R⁷ and R⁸ which are not substituents having from 4 to 3000 carbon atoms or polyisobutenyl radicals having a number-average molecular weight M_(n) of from 200 to 40 000 each independently represent hydrogen atoms, hydroxyl groups or, when they are hydrocarbyl radicals, usually relatively short-chain hydrocarbyl radicals having from 1 to 20, preferably from 1 to 12, in particular from 1 to 8, most preferably linear or branched C₁- to C₄-alkyl radicals. Typical examples of the latter are methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, sec-butyl and tert-butyl. In this context, very particular preference is given to methyl radicals and tert-butyl radicals.

Tetrahydrobenzoxazines I to be used with preference in accordance with the invention are also those in which the substituents R² and/or R⁴, when they are relatively short-chain hydrocarbyl radicals, represent linear or branched C₁- to C₄-alkyl radicals, especially methyl radicals and/or tert-butyl radicals. Of course, such substitution patterns are only possible for tetrahydrobenzoxazines having a total of one or two tetrahydrooxazine ring systems.

In the radical of the formula Y, the substituent X denotes a hydrocarbon bridging element which consists of one or more, preferably from 4 to 800, especially from 10 to 300, in particular from 12 to 100 isobutene units, or comprises one or more, preferably from 4 to 800, especially from 10 to 300, in particular from 12 to 100 isobutene units. When X consists of isobutene units, it is attached generally via the α- and the ω-carbon atom. When X comprises further hydrocarbon structural units, they are preferably initiator molecule structural units arranged in the middle, such as aromatic ring systems, for example o-, m- or p-phenylene units, and/or hydrocarbon structural units with functional groups for attachment, for example o-, m- or p-hydroxyphenyl groups, as the chain conclusion at both ends. Such telechelic polyisobutene systems underlying the substituents X and their preparation are described, for example, in U.S. Pat. No. 4,429,099 (7).

In the radical of the formula Z or Z′, the substituents R¹⁰ and R¹¹ preferably represent hydrogen and/or linear or branched C₁- to C₄-alkyl radicals, in particular methyl radicals. The compound I having a Z or Z′ radical, in which R¹⁰=R¹¹=methyl, derives from bisphenol A [2,2-bis(4-hydroxyphenyl)propane]. As a result of the preparation, compounds I having a Z radical and compounds I having the corresponding Z′ radical may also be present as mixtures.

Hydrocarbyl radicals having from 1 to 3000 or from 4 to 3000 carbon atoms for the substituents R¹, R², R³, R⁴, R⁵, R⁷ and R⁸ should be understood here to mean pure hydrocarbon radicals of any structure, which, by definition, may also be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties. In particular, hydrocarbyl radicals are alkyl, alkenyl, cycloalkyl, aryl, alkylaryl, alkenylaryl or arylalkyl radicals.

Interruptions in the hydrocarbyl radical by NR⁶ moieties also mean those radicals in which the NR⁶ moieties have been inserted formally into a C—H bond at the end, i.e., for example, substituents R¹, R², R³, R⁴, R⁵, R⁷ or R⁸ with an NH₂ end group. Such hydrocarbyl radicals derive, for example, from polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, etc., in which one of the terminal nitrogen atoms is the nitrogen atom in the oxazine ring.

The term “alkyl” comprises straight-chain and branched alkyl groups. Examples of the alkyl groups are, in addition to the methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, sec-butyl and tert-butyl radicals, in particular also n-pentyl, 2-pentyl, 2-methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1-ethyl-propyl, n-hexyl, 2-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethylbutyl, 2-ethylbutyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-heptyl, 3-heptyl, 2-ethylpentyl, 1-propylbutyl, n-octyl, 2-ethylhexyl, 2-propylheptyl, n-nonyl, n-decyl, n-dodecyl, n-tridecyl, isotridecyl, n-tetradecyl (myristyl), n-hexadecyl (palmityl), n-octadecyl (stearyl), and n-eicosyl.

Examples of alkenyl radicals are vinyl, 1-propenyl, 2-propenyl, oleyl, linolyl and linolenyl.

Examples of cycloalkyl radicals are C₅- to C₁-cycloalkyl groups such as cyclopentyl, cyclohexyl and cycloheptyl, which may also be substituted by alkyl groups, for example methyl radicals.

The term “aryl” comprises monocyclic, bicyclic, tricyclic and higher polycyclic aromatic hydrocarbon radicals. In the case of substitution by the alkyl and/or alkenyl radicals, for example those mentioned above, to give alkylaryl or alkenylaryl radicals, these aryl radicals may also bear 1, 2, 3, 4 or 5, preferably 1, 2 or 3 substituents. Typical examples are phenyl, tolyl, xylyl, mesityl, naphthyl, fluorenyl, anthracenyl, phenanthrenyl, naphthacenyl and styryl. A typical example of an arylalkyl radical is benzyl.

When the relatively long-chain hydrocarbyl radical having from 4 to 3000 carbon atoms is a polyisobutenyl radical, it may be based in principle on any common and commercially available polyisobutene, which is introduced in a suitable manner into the synthesis of the tetrahydrobenzoxazines I. Such a polyisobutene preferably has a number-average molecular weight M_(n) of at least 200. Preference is given to polyisobutenes having a number-average molecular weight M_(n) in the range from 200 to 40 000, more preferably from 500 to 15 000, in particular from 700 to 7000, especially from 900 to 3000 and most preferably from 900 to 1100. In the context of the present invention, the term “polyisobutene” also includes oligomeric isobutenes such as dimeric, trimeric, tetrameric, pentameric, hexameric and heptameric isobutene.

The polyisobutenyl radicals incorporated into the tetrahydrobenzoxazines I used in accordance with the invention preferably derive from so-called “high-reactivity” polyisobutene. “High-reactivity” polyisobutenes differ from the “low-reactivity” polyisobutenes by the content of terminal double bonds. Thus, high-reactivity polyisobutenes comprise at least 50 mol % of terminal double bonds based on the total number of polyisobutene macromolecules. Particular preference is given to polyisobutenes having at least 60 mol % and especially having at least 80 mol % of terminal double bonds based on the total number of polyisobutene macromolecules. The terminal double bonds may either be vinyl double bonds [—CH═C(CH₃)₂] (β-olefin) or vinylidene double bonds [—CH—C(═CH₂)—CH₃] (α-olefin). The substantially homopolymeric polyisobutene radicals also have uniform polymer backbones. Among these, preference is given in the context of the present invention to those polyisobutene systems which are formed to an extent of at least 85% by weight, preferably to an extent of at least 90% by weight and more preferably to an extent of at least 95% by weight from isobutene units of the repeat unit [—CH₂C(CH₃)₂—].

A further preferred feature of the polyisobutenes which can underly the tetrahydrobenzoxazines I used in accordance with the invention is that they are terminated by a tert-butyl group [—CH₂C(CH₃)₃] to an extent of at least 15% by weight, especially to an extent of at least 50% by weight, in particular to an extent of at least 80% by weight.

Moreover, the polyisobutenes preferably serving as the basis of the tetrahydrobenzoxazines I used in accordance with the invention preferably have a polydispersity index (PDI) of from 1.05 to 10, preferably from 1.05 to 3.0, in particular from 1.05 to 2.0. Polydispersity is understood to mean the quotient of weight-average molecular weight M_(w) and number-average molecular weight M_(n) (PDI=M_(w)/M_(n)).

In the context of the present invention, the polyisobutenes preferably serving as the basis of the tetrahydrobenzoxazines I used in accordance with the invention are also understood to mean all polymers which are obtainable by cationic polymerization and comprise, in copolymerized form, preferably at least 60% by weight of isobutene, more preferably at least 80% by weight, in particular at least 90% by weight and especially at least 95% by weight of isobutene. In addition, the polyisobutenes may comprise, in copolymerized form, further butene isomers such as 1- or 2-butene, and also different olefinically unsaturated monomers which are copolymerizable with isobutene under cationic polymerization conditions.

Suitable isobutene feedstocks for the preparation of polyisobutenes which can serve as the basis of the tetrahydrobenzoxazines I used in accordance with the invention are accordingly both isobutene itself and isobutenic C₄ hydrocarbon streams, for example C₄ raffinates, C₄ cuts from isobutene dehydrogenation, C₄ cuts from steamcrackers, FCC crackers (FCC: Fluid Catalyzed Cracking), provided that they have been substantially freed of 1,3-butadiene present therein. Particularly suitable C₄ hydrocarbon streams comprise generally less than 500 ppm, preferably less than 200 ppm of butadiene. When C₄ cuts are used as the starting material, the hydrocarbons other than isobutene assume the role of an inert solvent.

Useful monomers copolymerizable with isobutene include vinylaromatics such as styrene and α-methylstyrene, C₁-C₄-alkylstyrenes such as 2-, 3- and 4-methylstyrene, and also 4-tert-butylstyrene, isoolefins having from 5 to 10 carbon atoms such as 2-methylbutene-1,2-methylpentene-1,2-methylhexene-1,2-ethylpentene-1,2-ethylhexene-1 and 2-propylheptene-1.

Typical polyisobutenes which may serve as the basis of the tetrahydrobenzoxazines I used in accordance with the invention are, for example, the Glissopal® brands from BASF Aktiengesellschaft, for example Glissopal 550, Glissopal 1000 and Glissopal 2300, and also the Oppanol® brands from BASF Aktiengesellschaft, for example Oppanol B10, B12 and B15.

Examples of tetrahydrobenzoxazines I typical in the context of the present invention, with a tetrahydrooxazine ring on the benzene ring, are the following, where “PIB” represents a polyisobutenyl radical derived from a high-reactivity polyisobutene (M_(n) 1000) and “PIB*” is a polyisobutylene bridging element derived from a high-reactivity polyisobutene (M_(n) 870):

As a result of the preparation, it is also possible for mixtures in each case of the compounds VIa+XVa, VIb+XVb, VIIa+XVIa, VIIb+XVIb, VIII+XVII, IXa+XVIIIa, IXb+XVIIIb, Xa+XIXa, Xb+XIXb or XI+XX to occur, and to be used in this form in accordance with the invention.

In a preferred embodiment, tetrahydrobenzoxazines I in which the substituents R³ and R⁴ or R⁴ and R⁵, together with a part-structure —O—CH₂—NR⁷—CH₂-oxygen-attached via the substituent R⁴, form a second tetrahydrooxazine ring are used for the present invention. Examples thereof are the above-listed compounds VI to XX.

The tetrahydrobenzoxazines I described are used in accordance with the present invention as stabilizers for stabilizing inanimate organic material against the action of light, oxygen and heat. This is understood to mean in particular their mode of action as antioxidants in the conventional sense. To this end, the compounds are incorporated into the material to be stabilized during or after its production and distributed as homogeneously as possible. The concentration of these compounds in the organic material to be stabilized is generally from 0.0001 to 5% by weight, preferably from 0.001 to 5% by weight, in particular form 0.01 to 2% by weight, especially from 0.05 to 1% by weight, based on the organic material.

Inanimate organic material is understood to mean, for example, cosmetic preparations such as ointments and lotions, medicament formulations such as pills and suppositories, photographic recording materials, especially photographic emulsions, paints and plastics. They further include especially mineral oil products and fuels, for example diesel fuel, gasoline fuel, turbine fuel, motor or lubricant oils, gearbox oils and lubricant greases.

Examples of plastics which may be stabilized by the tetrahydrobenzoxazines I described include:

polymers of mono- or diolefins, such as low- or high-density polyethylene, polypropylene, linear polybutene-1, polyisoprene, polybutadiene, and also copolymers of mono- or diolefins or mixtures of the polymers mentioned;

polystyrene and copolymers of styrene or α-methylstyrene with dienes and/or acrylic derivatives, for example styrene-butadiene, styrene-acrylonitrile (SAN), styrene-ethyl methacrylate, styrene-butadiene-ethyl acrylate, styrene-acrylonitrile-methacrylate, acrylonitrile-butadiene-styrene (ABS) or methyl methacrylate-butadiene-styrene (MBS); halogen-containing polymers, for example polyvinyl chloride, polyvinyl fluoride, polyvinylidene fluoride and their copolymers; polymers which derive from α,β-unsaturated acids and their derivatives, such as polyacrylates, polymethacrylates, polyacrylamides and polyacrylonitriles; polymers which derive from unsaturated alcohols and amines or from their acyl derivatives or acetals, for example polyvinyl alcohol and polyvinyl acetate; polyurethanes, especially thermoplastic polyurethanes, polyamides, polyureas, polyphenylene ethers, polyesters, polycarbonates, polysulfones, polyethersulfones and polyetherketones.

The paints which can be stabilized with the tetrahydrobenzoxazines I described include coatings such as alkyd resin coating, dispersion coatings, epoxy resin coatings, polyurethane coatings, acrylic resin coatings and cellulose nitrate coatings, or varnishes such as wood protection varnishes.

The tetrahydrobenzoxazines I described are suitable in a particularly advantageous manner as stabilizers in turbine fuels (jet fuels). This is also understood to mean their mode of action as antioxidants in the conventional sense. In particular, by virtue of their mode of action as stabilizers, they serve to improve the thermal stability of turbine fuels. Moreover, especially also by virtue of their action as stabilizers, i.e. in their property as dispersants, they prevent deposits in the fuel system and/or combustion system of turbines. Turbine fuels are used in particular for operating aviation turbines.

The present invention further provides a turbine fuel composition which comprises a turbine fuel (jet fuel) and at least one of the tetrahydrobenzoxazines I described.

The inventive turbine fuel composition comprises a majority of a liquid turbine fuel, which is, for example, a turbine fuel customary in civilian or military aviation. These include, for example, fuels of the designation Jet Fuel A, Jet Fuel A-1, Jet Fuel B, Jet Fuel JP-4, JP-5, JP-7, JP-8 and JP-8+100. Jet A and Jet A-1 are commercially available turbine fuel specifications based on kerosene. The accompanying standards are ASTM D 1655 and DEF STAN 91-91. Jet B is a more highly cut fuel based on naphtha and kerosene fractions. JP-4 is equivalent to Jet B. JP-5, JP-7, JP-8 and JP-8+100 are military turbine fuels, as used, for example, by the Marines and Air Force. Some of these standards relate to formulations which already comprise further additives such as corrosion inhibitors, icing inhibitors, static dissipators, etc.

The tetrahydrobenzoxazines I described may be added to the turbine fuel or to the turbine fuel composition individually, as mixtures and, if appropriate, in combination with further additives known per se.

Suitable additives which may be present in the inventive turbine fuel composition comprise typically detergents, corrosion inhibitors, further antioxidants such as sterically hindered tert-butylphenols, n-butylphenylenediamines or N,N′-diphenylamine and derivatives thereof, metal deactivators such as N,N′-disalicylidene-1,2-diaminopropane, solubilizers, antistats such as Stadis 450, biocides, anti-icing agents such as diethylene glycol methyl ether, and also mixtures of the additives mentioned.

Additives preferred in the context of the present invention are the specific compound classes (A), (B) and (C) detailed below:

Preferred additives (A) are compounds which derive from succinic anhydride and have long-chain hydrocarbon radicals having generally from 15 to 700, in particular from 30 to 200 carbon atoms. These compounds may have further functional groups which are preferably selected from hydroxyl, amino, amido and/or imido groups. Preferred additives are the corresponding derivatives of polyalkenylsuccinic anhydride which are obtainable, for example, by reacting polyalkenes with maleic anhydride by a thermal route or via the chlorinated hydrocarbons. The number-average molecular weight of the long-chain hydrocarbon radicals is preferably in a range from about 200 to 10 000, more preferably from 400 to 5000, in particular from 600 to 3000 and especially from 650 to 2000. These long-chain hydrocarbon radicals preferably derive from conventional polyisobutenes and especially from the aforementioned reactive polyisobutenes. Of particular interest as additives (A) are the derivatives of polyalkenylsuccinic anhydrides with ammonia, monoamines, polyamines, monoalcohols and polyols. Polyamines preferred for derivatization comprise ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, propylenediamine, etc. Suitable alcohols comprise monohydric alcohols such as ethanol, allyl alcohol, dodecanol and benzyl alcohol, polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, 1,2-butanediol, neopentyl glycol, glycerol, trimethylolpropane, erythritol, pentaerythritol, mannitol and sorbitol.

Succinic anhydride derivatives (A) suitable as additives are described, for example, in U.S. Pat. No. 3,522,179, U.S. Pat. No. 4,234,435, U.S. Pat. No. 4,849,572, U.S. Pat. No. 4,904,401, U.S. Pat. No. 5,569,644 and U.S. Pat. No. 6,165,235, which is fully incorporated here by reference.

Preferred additives (B) are polyalkenylthiophosphonate esters. The polyalkenyl radical of these esters preferably has a number-average molecular weight in the range from about 300 to 5000, more preferably from 400 to 2000 and in particular form 500 to 1500. The polyalkenyl radical derives preferably from polyolefins as have already been described as long-chain hydrocarbon radical for component (A). They are especially polyalkenyl radicals which derive from conventional or reactive polyisobutenes. Suitable processes for preparing suitable polyalkenylthiophosphonate esters by reacting a polyolefin with a thiophosphorylating agent are described, for example, in U.S. Pat. No. 5,725,611, which is incorporated here by reference.

Preferred additives (C) are Mannich adducts. Such additives are obtained in principle by Mannich reaction of aromatic hydroxyl compounds, especially phenol and phenol derivatives, with aldehydes and mono- or polyamines. They are preferably the reaction products of polyisobutene-substituted phenols with formaldehyde and mono- or polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dimethylaminopropylamine, etc. Suitable Mannich adducts and processes for their preparation are described, for example, in U.S. Pat. No. 5,876,468, EP-A 831 141, EP-A 1 233 990 and EP-A 1 226 188, which are incorporated here by reference.

The inventive turbine fuel composition comprises the tetrahydrobenzoxazines I described in an amount of typically from 0.0001 to 1% by weight, preferably from 0.001 to 0.5% by weight, especially from 0.01 to 0.2% by weight and in particular from 0.01 to 0.1% by weight, based on the total amount of the turbine fuel composition.

The additives (A) to (C) and, if appropriate, further additives from those mentioned above may typically each be used in amounts of in each case from 0.0001 to 1% by weight, preferably from 0.001 to 0.6% by weight and in particular from 0.0015 to 0.4% by weight, based on the total amount of the turbine fuel composition.

The present invention further provides an additive concentrate for turbine fuels (jet fuels) which comprises at least one of the tetrahydrobenzoxazines I described and, if appropriate, at least one diluent and, if appropriate, at least one further additive which is preferably selected from those described above. In a preferred embodiment, the inventive additive concentrate, and hence also the inventive turbine fuel composition, comprises one or more additives from the group of (A), (B) and (C), especially also mixtures thereof such as (A)+(B), (A)+(C), (B)+(C) and (A)+(B)+(C).

Suitable diluents are, for example, fractions obtained in crude oil processing, such as kerosene, naphtha or brightstock. Also suitable are aromatic and aliphatic hydrocarbons such as Solvent Naphtha heavy, Solvesso® or Shellsol®, and also mixtures of these solvents and diluents.

The tetrahydrobenzoxazines I described are present in the inventive additive concentrate preferably in an amount of from 0.1 to 100% by weight, more preferably from 1 to 80% by weight and in particular from 10 to 70% by weight, based on the total weight of the concentrate.

The present invention also provides a process for preparing tetrahydrobenzoxazines I, which comprises reacting an appropriately substituted phenol, pyrocatechol, resorcinol, hydroquinone, phloroglucinol or hydroxyhydroquinone with a reagent, preformed from one mole of a primary amine of the formula R¹—NH₂ or R⁷—NH₂ or R⁸—NH₂, two moles of formaldehyde or of a formaldehyde-releasing substance and two moles of a linear or branched C₁- to C₈-alcohol of the formula R⁹—OH, of the general formula II

in which A is the substituents R¹, R⁷ or R⁸ which are each as defined above, under suitable conditions. Depending on the desired number of tetrahydrooxazine rings and of hydroxyl groups present on the benzene ring, the aromatic hydroxyl compound can be reacted here with 1, 2 or 3 equivalents of reagent II. The resulting tetrahydrobenzoxazine I, as described above, has at least one hydrocarbyl radical which has from 4 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties.

Suitable linear or branched C₁- to C₈-alcohols of the formula R⁹—OH are in particular linear or branched C₁- to C₈-alkanols such as methanol, ethanol, isopropanol, isobutanol and sec-butanol.

Suitable conditions for the reaction of the aromatic hydroxyl compounds with the reagent II are, for example, temperatures of from 0 to 130° C., in particular from 20 to 100° C. It is appropriate to work in an inert organic solvent, especially an aromatic hydrocarbon such as toluene or xylene.

The reagent II is typically prepared from the feedstocks specified by distilling off the water freed in the course of its formation. A suitable method for this purpose is, for example, heating in a water-separating inert organic solvent, especially an aromatic hydrocarbon such as toluene or xylene. However, the water released can in principle also remain in the reagent II where it does not disrupt the further reactions. The formaldehyde-releasing substance used may, for example, be paraformaldehyde.

The preparation process according to the invention has the advantage that the desired tetrahydrobenzoxazine I is obtained in high yield, i.e. substantially without undesired by-products or at least in highly enriched form.

In some cases, the desired tetrahydrobenzoxazine I can be obtained in appropriate purity even without preceding provision of the reagent II, by direct reaction of the appropriately substituted aromatic hydroxyl compound with one mole of a primary amine of the formula R¹—NH₂ or R⁷—NH₂ or R⁸—NH₂ and two moles of formaldehyde or of a formaldehyde-releasing substance (per hydroxyl group to be converted), the reaction being carried out, if appropriate, in a suitable solvent such as an alcohol, for example a linear or branched C₁- to C₈-alcohol of the formula R⁹—OH. In this method, however, there is the risk in principle that, depending on the reactant structure, stoichiometry and reaction conditions, not inconsiderable amounts of undesired open-chain conventional Mannich adducts can form from aromatic hydroxyl compound, amine and formaldehyde.

Since some of the tetrahydrobenzoxazines I described are novel substances, these novel substances themselves also form part of the subject matter of the present invention.

Tetrahydrobenzoxazines I in which the relatively long-chain hydrocarbyl radical(s) having in each case from 20 to 3000 carbon atoms are present as substituents on the nitrogen atoms of the tetrahydrooxazine rings are novel. The present invention therefore also provides tetrahydrobenzoxazines of the general formula Ia

in which the substituent R¹ represents a hydrocarbyl radical which has from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where R⁶ represents a hydrogen atom or a C₁- to C₄-alkyl radical, and the substituents R², R³, R⁴ and R⁵ are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where the substituent R⁴ may also be a radical of the formula Y

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituent X is a hydrocarbon bridging element which consists of one or more isobutene units or comprises one or more isobutene units, or where the substituent R⁴ may also be a radical of the formula Z or Z′

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituents R¹⁰ and R¹¹ may be the same or different and represent hydrogen or a C₁- to C₁₀-alkyl radical, and in which the substituents R² and R³ or R³ and R⁴ or R⁴ and R⁵, together with the part-structure —O—CH₂—NR⁷—CH₂— attached to the benzene ring, may also form a second tetrahydrooxazine ring, or the substituents R² and R³ and R⁴ and R⁵, together with the part-structures —O—CH₂—NR⁷—CH₂— and —O—CH₂—NR⁸—CH₂— attached to the benzene ring, may also form a second and a third tetrahydrooxazine ring, where R⁷ and R⁸ are each independently hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, with the proviso that at least one of the substituents R¹ or R⁷ or R⁸ has from 20 to 3000 carbon atoms and the remaining substituents from the group of R¹, R², R³, R⁴, R⁵, R⁷ and R⁸, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms.

Tetrahydrobenzoxazines I having hydroxyl groups which are in the 2- and/or 4-position on the benzene ring, and having relatively long-chain hydrocarbyl radicals having in each case from 4 to 3000 carbon atoms as substituents on the nitrogen atoms of the tetrahydrooxazine rings are novel. The present invention therefore also provides tetrahydrobenzoxazines of the general formula Ib

in which the substituent R¹ represents a hydrocarbyl radical which has from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where R⁶ represents a hydrogen atom or a C₁- to C₄-alkyl radical, and the substituents R², R³, R⁴ and R⁵ are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where the substituent R⁴ may also be a radical of the formula Y

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituent X is a hydrocarbon bridging element which consists of one or more isobutene units or comprises one or more isobutene units, or where the substituent R⁴ may also be a radical of the formula Z or Z′

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituents R¹⁰ and R¹¹ may be the same or different and represent hydrogen or a C₁- to C₁₀-alkyl radical, and in which the substituents R² and R³ or R³ and R⁴ or R⁴ and R⁵, together with the part-structure —O—CH₂—NR⁷—CH₂— attached to the benzene ring, may also form a second tetrahydrooxazine ring, where R⁷ is a hydrocarbyl radical which has from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, with the proviso that at least one of the substituents R¹ or R⁷ has from 4 to 3000 carbon atoms and the remaining substituents from the group of R¹, R², R³, R⁴, R⁵ and R⁷, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms, and with the proviso that the substituents R² and/or R⁴ are hydroxyl groups.

Tetrahydrobenzoxazines I having a tetrahydrooxazine ring in which the relatively long-chain hydrocarbyl radical(s) are certain polyisobutenyl radicals and/or certain alk(en)yl radicals and are in the 2- and/or 4-position on the benzene ring and the alkyl radical has from 1 to 4 carbon atoms on the nitrogen atom are novel. The present invention therefore also provides tetrahydrobenzoxazines of the general formula Ic

in which the substituent R¹ represents a C₁- to C₄-alkyl radical, the substituents R² and/or R⁴ are each independently C₁₆- to C₂₀-alkyl or -alkenyl radicals and/or polyisobutenyl radicals having a number-average molecular weight M_(n) of from 900 to 3000 and the substituents R³ and R⁵ are each hydrogen.

Tetrahydrobenzoxazines I which have a second tetrahydrooxazine ring or a second and a third tetrahydrooxazine ring on the benzene ring are novel. The present invention therefore also provides tetrahydrobenzoxazines of the general formula Id

in which the substituent R¹ represents a hydrocarbyl radical which has from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where R⁶ represents a hydrogen atom or a C₁- to C₄-alkyl radical, and the substituents R², R³, R⁴ and R⁵ are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁶ moieties, where the substituent R⁴ may also be a radical of the formula Y

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituent X is a hydrocarbon bridging element which consists of one or more isobutene units or comprises one or more isobutene units, or where the substituent R⁴ may also be a radical of the formula Z or Z′

in which the substituents R¹, R², R³ and R⁵ are each as defined above and the substituents R¹⁰ and R¹¹ may be the same or different and represent hydrogen or a C₁- to C₁₀-alkyl radical, and in which the substituents R² and R³ or R³ and R⁴ or R⁴ and R⁵, together with the part-structure —O—CH₂—NR⁷—CH₂— attached to the benzene ring, may form a second tetrahydrooxazine ring, or the substituents R² and R³ and R⁴ and R⁵, together with the part-structures —O—CH₂—NR⁷—CH₂— and —O—CH₂—NR⁸—CH₂— attached to the benzene ring, may form a second and a third tetrahydrooxazine ring, where R⁷ and R⁸ are each independently hydrocarbyl radicals which have in each case from 1 to 3000 carbon atoms and may be interrupted by one or more heteroatoms from the group of O and S and/or by one or more NR⁸ moieties, with the proviso that at least one of the substituents R¹, R², R³, R⁴, R⁵, R⁷ or R⁸ has from 4 to 3000 carbon atoms and the remaining substituents from the group of R¹, R², R³, R⁴, R⁵, R⁷ and R⁸, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms.

The invention will be illustrated in detail with reference to the nonlimiting examples which follow.

Preparation Examples Example 1 N,N-Di(Isobutoxymethyl)-N-Methylamine (Reagent of the Formula II)

A 2 l four-neck flask with water separator was initially charged with 600 ml of isobutanol and 90 g of paraformaldehyde. 113 g of a 41% by weight aqueous methylamine solution were then added dropwise over 12 minutes, in the course of which the temperature rose to 44° C. After addition of 200 ml of toluene, the mixture was heated under vigorous reflux, in the course of which 126 ml of water separated out. Low boilers were distilled off on a rotary evaporator at 60° C. and 15 mbar. 244 g of product were obtained in the form of a light, clear liquid with amine-like odor.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.23 ppm, 4H, CH₃—N[CH ₂—O—CH₂—CH(CH₃)₂]₂     -   δ=3.17 ppm, 4H, CH₃—N[CH₂—O—CH ₂—CH(CH₃)₂]₂     -   δ=2.55 ppm, 3H, CH ₃—N[CH₂—O—CH₂—CH(CH₃)₂]₂     -   δ=1.83 ppm, 2H, CH₃—N[CH₂—O—CH₂—CH(CH₃)₂]₂     -   δ=0.91 ppm, 12H, CH₃—N[CH₂—O—CH₂—CH(CH ₃)₂]₂

Example 2 Tetrahydrobenzoxazine of the Formula Vc

A 500 ml four-neck flask was initially charged with 30 g of paraformaldehyde at room temperature in 100 ml of isopropanol. 142 g of molten n-octadecylamine were added rapidly. The flask contents were heated to reflux and stirred under reflux for 30 minutes. 76 g of trimethyihydroquinone were added in 3 portions within 15 minutes. The mixture was stirred under reflux for 30 minutes. In the course of cooling to room temperature, a solid precipitated out and was filtered off with suction through a D3 suction filter. The filter residue was washed repeatedly with heptane. Subsequently, the residue was dried overnight in a vacuum drying cabinet at 50° C. and 100 mbar under nitrogen atmosphere. 186.4 g of product were obtained.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.70 ppm, 2H, —CH₂—N(CH₃)—CH ₂—O—     -   δ=3.82 ppm, 2H, —CH ₂—N(CH₃)—CH₂—O—

Example 3 Tetrahydrobenzoxazines of the Formulae VIa+XVa

A 500 ml four-neck flask was initially charged with 30 g of paraformaldehyde at room temperature in 100 ml of isopropanol. 142 g of molten n-octadecylamine were added rapidly. The flask contents were heated to reflux and stirred under reflux for 30 minutes. 27.5 g of hydroquinone were added in 3 portions within 15 minutes. The mixture was stirred under reflux for 30 minutes. In the course of cooling to room temperature, a solid precipitated out and was filtered off with suction through a D3 suction filter. The filter residue was washed repeatedly with heptane. Subsequently, the residue was dried overnight in a vacuum drying cabinet at 50° C. and 100 mbar under a nitrogen atmosphere. 30 g of product were obtained in the form of a mixture of VIa+XVa. The filtrate was concentrated by evaporation at 140° C. and 5 mbar. 145 g of further product were obtained in the form of a mixture of VIa+XVa.

1H NMR (400 MHz, 16 scans, CDCl₃):

VIa:

-   -   δ=4.70 ppm, 2H, —CH₂—N(C₁₈H₃₇)—CH ₂—O—     -   δ=3.73 ppm, 2H, —CH ₂—N(C₁₈H₃₇)—CH₂—O—         XVa:     -   δ=4.74 ppm, 2H, —CH₂—N(C₁₈H₃₇)—CH ₂—O—     -   δ=3.86 ppm, 2H, —CH ₂—N(C₁₈H₃₇)—CH₂—O—

The integrals of the spectra give rise to the following weight ratios:

VIa:XVa in the residue: 9:1

VIa:XVa in the filtrate: 1:1

Example 4 Tetrahydrobenzoxazine of the Formula IIIa

A 2000 ml four-neck flask was initially charged with 615 g of 2-methyl-4-polyisobutenylphenol (based on the commercially available high-reactivity polyisobutene Glissopal® 1000 with an Mn of 1000) at room temperature in 500 ml of toluene. 107 g of N,N-di(isobutoxymethyl)-N-methylamine from example 1 were added rapidly. The flask contents were stirred at 80° C. for 30 minutes. The solution was concentrated by evaporation at 120° C. and 5 mbar. 650 g of product were obtained in the form of an oil which can then be washed with methanol to remove small amounts of amine/aldehyde condensation products formed as a by-product.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.73 ppm, 2H, —CH₂—N(CH₃)—CH ₂—O—     -   δ=3.87 ppm, 2H, —CH ₂—N(CH₃)—CH₂—O—

Example 5 Tetrahydrobenzoxazine of the Formula IIIe

A 1000 ml four-neck flask was initially charged with 206 g of 2,4-di-tert-butylphenol at room temperature in 400 ml of toluene. 203 g of N,N-di(isobutoxymethyl)-N-methylamine from example 1 were added rapidly. The flask contents were stirred at 80° C. for 60 minutes. The solution was concentrated by evaporation at 120° C. and 5 mbar. 260 g of product were obtained.

1H NMR (400 MHz, 16 scans, CD₂Cl₂):

-   -   δ=4.73 ppm, 2H, —CH₂—N(CH₃)—CH ₂—O—     -   δ=3.90 ppm, 2H, —CH ₂—N(CH₃)—CH₂—O—

Example 6 Tetrahydrobenzoxazines of the Formulae VIII+XVII

A 2000 ml four-neck flask was initially charged with 24 g of paraformaldehyde at room temperature in 200 ml of isobutanol. 615 g of Kerocom® PIBA (commercially available 65% by weight solution of polyisobutenylamine based on high-reactivity polyisobutene, Mn=1000, in Mihagol, an n-alkane mixture) were added rapidly. The flask contents were heated to reflux and stirred under reflux for 30 minutes. 200 ml of toluene were then added and the water formed was entrained out. 22 g of hydroquinone were added dissolved in 200 ml of n-butanol within 15 minutes. Subsequently, the mixture was stirred under reflux for 60 minutes. The solution was concentrated by evaporation at 140° C. and 5 mbar. 440 g of product were obtained.

1H NMR (400 MHz, 16 scans, CDCl₃):

VIII:

-   -   δ=4.70 ppm, 2H, —CH₂—N(PIB)-CH ₂—O—     -   δ=3.73 ppm, 2H, —CH ₂—N(PIB)-CH₂—O—         XVII:     -   δ=4.75 ppm, 2H, —CH₂—N(PIB)-CH ₂—O—     -   δ=3.87 ppm, 2H, —CH ₂—N(PIB)-CH₂—O—

The integrals of the spectra give rise to the following weight ratios:

VIII:XVII=1:1.1.

Example 7 Tetrahydrobenzoxazine of the Formula IIIb

A 2000 ml four-neck flask was initially charged with 550 g of 4-polyisobutenylphenol (based on the commercially available high-reactivity polyisobutene Glissopal® 1000 with an Mn of 1000) at room temperature in 500 ml of toluene. 107 g of N,N-di-(isobutoxymethyl)-N-methylamine from example 1 were added rapidly. The flask contents were stirred at 80° C. for 60 minutes. The solution was washed with methanol and concentrated by evaporation at 120° C. and 5 mbar. 517 g of product were obtained.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.72 ppm, 2H, —CH₂—N(CH₃)—CH ₂—O—     -   δ=3.90 ppm, 2H, —CH ₂—N(CH₃)—CH₂—O—

Example 8 Tetrahydrobenzoxazine of the Formula Vd

A 4000 ml four-neck flask was initially charged with 52.8 g of paraformaldehyde at room temperature in 400 ml of isopropanol. 1990 g of Kerocom® PIBA (commercially available 65% by weight solution of polyisobutenylamine based on high-reactivity polyisobutene, Mn=1000, in Mihagol, an n-alkane mixture) were added within 78 minutes. The flask contents were heated to reflux and stirred under reflux for 40 minutes. Thereafter, 138.1 g of trimethylhydroquinone were added in portions at from 60 to 80° C. Subsequently, 100 ml of toluene were added and the mixture was heated under reflux for 2 hours. Once the mixture had been cooled to room temperature and the isopropanol phase had then been removed and discarded, 1000 ml of heptane were added. The solution was washed with water and methanol and dried over sodium sulfate. The dry solution was concentrated by evaporation at 140° C. and 5 mbar. 1414 g of product were obtained.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.70 ppm, 2H, —CH₂—N(PIB)-CH ₂—O—     -   δ=3.81 ppm, 2H, —CH ₂—N(PIB)-CH₂—O—     -   δ=2.12, 2.07 and 2.00 ppm, each 3H, —CH₃ on the aromatic

Example 9 Tetrahydrobenzoxazine of the Formula XXIIIa

A 500 ml four-neck flask was initially charged with 110 g of α,ω-bis(4-hydroxyphenyl)-polyisobutene with a central p-phenylene structural unit (Mn=2000) which had been prepared according to document (7) at room temperature in 100 ml of toluene. 21.5 g of N,N-di(isobutoxymethyl)-N-methylamine from example 1 were added rapidly. The flask contents were stirred at 80° C. for 60 minutes. The solution was washed with methanol and concentrated by evaporation at 80° C. and 5 mbar. 104 g of product were obtained.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.71 ppm, 2H, —CH₂—N(CH₃)—CH ₂—O—     -   δ=3.88 ppm, 2H, —CH ₂—N(CH₃)—CH₂—O—

Example 10 Tetrahydrobenzoxazine of the Formula IIIf

A 2000 ml four-neck flask was initially charged with 24 g of paraformaldehyde at room temperature in 150 ml of isopropanol. 800 g of Kerocom® PIBA (commercially available 65% by weight solution of polyisobutenylamine based on high-reactivity polyisobutene, Mn=1000, in Mihagol, an n-alkane mixture) were added within 20 minutes. The flask contents were heated to reflux and stirred under reflux for 30 minutes. Thereafter, 66 g of 2-tert-butyl-4-methylphenol dissolved in 150 ml of isopropanol were added dropwise. Subsequently, the mixture was heated under reflux for another 2 hours. Once the mixture had been cooled to room temperature and the isopropanol phase had then been removed and discarded, the solution was concentrated by evaporation at 140° C. and 5 mbar. 574 g of product were obtained.

1H NMR (400 MHz, 16 scans, CDCl₃):

-   -   δ=4.80 ppm, 2H, —CH₂—N(PIB)-CH ₂—O—     -   δ=3.90 ppm, 2H, —CH ₂—N(PIB)-CH₂—O—     -   δ=2.12 ppm, 3H, —CH₃ on the aromatic

Use Examples Example 11 Testing of the Thermal Stability of Turbine Fuel (Jet Fuel)

A turbine fuel of the specification Jet A according to ASTM D 1655 was used. The additization was effected with 100 mg/l of the tetrahydrobenzoxazines or tetrahydrobenzoxazine mixtures from preparation examples 4 and 6 to 10.

In a three-neck flask which had been equipped with stirrer, reflux condenser and thermometer, 5 l of air were first passed at room temperature through 150 ml of the fuel to be examined within 1 h. Subsequently, the fuel was heated to 140° C. with an oil bath and stirred at this temperature for a further 5 h. After cooling to room temperature, the entire amount of fuel was filtered through a 0.45 μm membrane filter. Subsequently, the filter residue was determined gravimetrically after drying in a drying cabinet at 115° C. for 45 min and subsequently drying under reduced pressure in a desiccator for 2 hours:

Blank value (without additive): 12.0 mg

additized in accordance with the invention with 100 mg/l in each case of the following compounds:

Compound of the formula IIIa (preparation example 4): 4.6 mg

Compounds of the formulae VIII=XVII (preparation example 6): 2.1 mg

Compound of the formula IIIb (preparation example 7): 2.4 mg

Compound of the formula Vd (preparation example 8): 2.2 mg

Compound of the formula XXIIIa (preparation example 9): 1.5 mg

Compound of the formula IIIf (preparation example 10): 1.0 mg

The use of the inventive additive distinctly reduced the amount of particles formed by thermal stress on the turbine fuel.

Example 12 Improvement in the Thermal Stability of Turbine Fuel (Jet Fuel)

A turbine fuel based on the specification Jet A according to ASTM D 1655 was used.

The thermal stability was tested according to the JFPOT breakpoint method according to ASTM D 3241. For the unadditized turbine fuel, a value of 240° C. was determined. With fuels which had each been additized with 100 mg/l in each case of an additive used in accordance with the invention and listed below, the following values were measured:

Compound of the formula IIIa (preparation example 4): 280° C.

Compound of the formula IIIb (preparation example 7): 270° C.

Compound of the formula Vd (preparation example 8): 270° C.

Compound of the formula XXIIIa (preparation example 9): 270° C.

Example 13 Testing of the Water Compatibility of Turbine Fuel

A turbine fuel of the specification Jet A-1 according to DEF STAN 91-91 was used.

According to DIN 51415 and ASTM D 1094, the water compatibility of the turbine fuel and hence the undesired tendency to form emulsions were determined after addition of 100 mg/l of the product from preparation example 6. To this end, 80 ml of the additized turbine fuel and 20 ml of water were agitated intensively in a defined manner. Thereafter, the phase separation layers were assessed visually after each of 1, 5, 30 and 60 minutes. As early as 5 minutes after addition of water, full separation of fuel and water was obtained; no emulsion fractions remained.

A repetition with 100 mg/l of the product from preparation example 7 led to the same result.

Example 14 Testing of the Water Separation Properties of Turbine Fuel

A turbine fuel of the specification Jet A-1 according to DEF STAN 91-91 was used. The tendency of turbine fuels with regard to their water separation properties was tested according to ASTM D 3948 (“MSEP” test). A characteristic feature of these measurements is the use of a standard coalescence filter with final opacity measurement of the fuel phase. In the measurement, the additives used in accordance with the invention were tested in combination with the antioxidant 2,6-di-tert-butyl-4-methylphenol (“BHT”) and the metal deactivator N,N′-disalicylidene-1,2-diaminopropane in a solvent customary for this purpose. The dosage of the additives used in accordance with the invention was in each case 215 mg/l (based on their 100% active substance content). The following ratings for the opacity behavior were determined [relative rating scale from 0 (worst mark) to 100 (best mark)]:

Blank value (without additive): 99

Compound of the formula IIIa (preparation example 4): 95

Compound of the formula IIIb (preparation example 7): 99

Compound of the formula Vd (preparation example 8): 94

No deteriorations in comparison with unadditized turbine fuel occurred. 

What is claimed is:
 1. A method to operate a turbine engine, comprising: adding a tetrahydrobenzoxazine of formula I to a liquid turbine fuel comprising kerosene to obtain a stabilized turbine fuel;

supplying the turbine engine with the stabilized turbine fuel through fuel lines; and combusting the stabilized fuel in the turbine; wherein the liquid turbine fuel is selected from the group consisting of Jet Fuel A, Jet Fuel A-1, Jet Fuel B, Jet Fuel JP-4, JP-5, JP-7, JP-8 and JP-8+100 according to ASTM D 1655 and DEF STAN 91-91, and wherein in formula (I) R¹ is a hydrocarbyl radical selected from the group consisting of a C₁₆ to C₂₀ alkenyl group and a polyisobutenyl group having a number-average molecular weight of from 200 to 40,000, R⁶ is a hydrogen atom or a C₁- to C₄-alkyl radical, and R², R³, R⁴ and R⁵ are each independently a hydrogen atom, a hydroxyl group or a hydrocarbyl group having from 1 to 3000 carbon atoms optionally substituted with one or more moieties selected from the group consisting of O, S and NR⁶ R⁴ may optionally be a radical of formula Y:

wherein R¹, R², R³ and R⁵ are each as defined above and X is a hydrocarbon bridging element which consists of one or more isobutene units or comprises one or more isobutene units, or R⁴ may also be a radical of formula Z or Z′

wherein R¹, R², R³ and R⁵ are each as defined above and R¹⁰ and R¹¹ are each independently hydrogen or a C₁- to C₁₀-alkyl radical, R² and R³ or R³ and R⁴ or R⁴ and R⁵, together with the part-structure —O—CH₂—NR⁷—CH₂— attached to the benzene ring, optionally form a second tetrahydrooxazine ring, or the substituents R² and R³ and R⁴ and R⁵, together with the part-structures —O—CH₂—NR⁷—CH₂- and —O—CH₂—NR⁸—CH₂— attached to the benzene ring, optionally form a second and a third tetrahydrooxazine ring, and R⁷ and R⁸ are each independently a hydrocarbyl group selected from the group consisting of a C₁₆ to C₂₀ alkenyl group and a polyisobutenyl group having a number-average molecular weight of from 200 to 40,000, with the proviso that R², R³, R⁴, R⁵, when they are hydrocarbyl radicals, each have from 1 to 20 carbon atoms.
 2. The method of claim 1, wherein at least one of R², R³, R⁴, R⁵, R⁷ and R⁸ is a polyisobutenyl group having a number-average molecular weight M_(n) of from 200 to 40
 000. 3. The method of claim 2, wherein at least one of R², R⁴, R⁷ and R⁸ is a polyisobutenyl group having a number-average molecular weight M_(n) of from 200 to 40
 000. 4. The method of claim 1, wherein the members of the group consisting of R², R³, R⁴, R⁵, R⁷ and R⁸ which are not substituents having from 4 to 3000 carbon atoms or polyisobutenyl radicals having a number-average molecular weight M_(n) of from 200 to 40 000 each independently is hydrogen atoms, hydroxyl or a linear or branched C₁- to C₄-alkyl.
 5. The method of claim 1, wherein R³ and R⁴ or R⁴ and R⁵, together with a part-structure —O—CH₂—NR⁷—CH₂— oxygen-attached via the substituent R⁴ form a second tetrahydrooxazine ring.
 6. The method of claim 1 wherein a content of the tetrahydrobenzoxazine of formula I is from 0.0001 to 1% by weight of the turbine fuel.
 7. The method of claim 6, further comprising adding at least one additive to the turbine fuel, wherein the additive is selected from the group consisting of a polyalkenylsuccinic anhydride, a polyalkenylthiophosphonate ester and a Mannich adduct of an aromatic hydroxyl compound with an aldehyde and a monoamine or a diamine.
 8. The method of claim 7 wherein a content of each additive in the turbine fuel is from 0.0001 to 1% by weight. 